Ammoniacal ammonium nitrate solution with hydrogen peroxide as corrosion inhibitor



ited rates Patent @ftice dfilbfi l Patented Feb. 5, 1963 No (let. 3. 3.953, der. No.

6 Claims. ((Il. 296-84) My invention relates to the corrosion of ferrous metals. .lore specifically, my invention relates to a composition consisting essentially of aqueous ammonia, ammonium nitrate and hydrogen peroxide said composition having reduced corrosion tendencies toward metal surfaces.

There is a well recognized corrosion problem in industries concerned with the manufacture, storage, transportation and handlin of ammonia-ammonium nitrate aqueous solution. In the handling of this solution it is often necessary to transport and store it in metal containers such as drums, tanks, and pipelines. These containers often have varying amounts of contaminants such as water and the like which tend to increase corrosion to ferrous metal surfaces. Storage and transportation present a favorable situation for contamination of aqueous ammonia-ammonium nitrate solutions with ma erials such as those containing sulfur. Even slight contamination has been found to cause rapid corrosion and the formation of rust.

This corrosion has resulted in the use of costly aluminum processing, sto -ng and handling equipment and the application of scmce and costly internal coatings to container walls in order to reduce corrosion.

Corrosion inhibitors of one type or another have been suggested and attempted with varying degrees of limited success. An example of such an inhibitor is ammonium thiocyanate which has been found to be relatively unsuccessful and thus generally abandoned. Sodium silicate, another supposed inhibitor, is ineffective and at times has permitted immediate and rapid corrosive attacks.

Other corrosion problems have arisen regarding the use of equipment when contacted with aqueous ammoniaamrnonium nitrate solutions in fertilizer plants. The presence of said solutions causes destructive corrosion to the equipment utilized in handling, storage and shipment of fertilizer products. An aqueous ammonia-ammonium nitrate solution in a reasonably pure state is mildly corrosive but in the presence of small amounts of corrosive constituents, i.e. about .05% by weight or more, there is im mediate and rapid attack on ferrous metal surfaces. As a practical matter such corrosive constituents are normally found in common commercial plants such as fertilizer plants which produce this solution. The contaminants are in general at least somewhat soluble sulfur constituents either organic or inorganic. Examples of these are sodium sulfide, sodium suliite, butyl mercaptans and sodium salts of butyl mercaptans.

in my invention 1 have found a new composition consisting essentially of aqueous ammonia-ammonium nitrate solution having hydrogen peroxide incorporated therein. My composition has reduced corrosion tendencies towards metal surfaces such as steel. The aqueous ammonia-ammonium nitrate solution utilized in my invention can be prepared by the addition of commercial ammonium hydroxide to ammonium nitrate with a subsequent addition or" water. The percent of ammonium hydroxide may vary with the desired properties peculiar to each solution. The preferred amount of ammonium hydroxide is about 10 to 35% by weight of the final composition. The amount of ammonium nitrate in my composition may vary from about 1 to 35% by Weight of the final composition. Cornmercial hydrogen peroxide can be utilized in my composition and will usually be about 0.0001 to 3% or more (H 0 basis) of the composition by weight with a preferred amount being about .001 to 0.3% by weight.

I conducted various tests under static conditions at room temperature using mild steel coupons having twothirds of their length immersed in various solutions. Each test started with ml. of solution in a 4 02. square jar with the coupon upright therein. The initial series of tests used bright, polished cold-rolled steel coupons. In the later tests hot-rolled steel coupons were used each having a mill-scaled side and edge and the other surfaces polished. In each of the examples there was employed an aqueous solution of 24% ammonium hydroxide, 4% of ammonium nitrate and .14% of varying supposed inhibitor or hydrogen peroxide.

EXAMPLE I A composition containing aqueous ammonia-ammonium nitrate and sodium silicate was tested according to the above and found to be corrosive with an immediate attack of rust on the steel coupons, and after 3 days of exposure, the rate of corrosion of the coupon was measured at 2278 rndd. which corresponds to' a rust penetration of inch in a nine month period. Mdd. is milligrams weight loss per square decimeter of exposed surface per day of exposure.

EXAMPLE II A composition containing ammonium thiocyanate and the aqueous ammonia-ammonium nitrate solution was tested according to the above and heavy rust on the immersed steel coupons appeared at the end of a 15 week period.

EXAMPLE 111 Using the above testing procedure, an octadecyl amineaqueous ammonia-ammonium nitrate solution was tested for corrosive tendencies. During an 18 week testing period, heavy rusting occurred thus showing the composition to be inetlective in inhibiting corrosion.

EXAMPLE IV Similarly a potassium chromate-aqueous ammonia-ammonium nitrate solution was tested and found to be corrosive when in contact with a steel coupon such as described above and medium rust occurred during an 18 week testing period.

EXAMPLE V Using the above testing procedure, a hydrogen sulfideaqueous ammonia-ammonium nitrate solution was applied to a steel coupon and a black coating appeared on. the metallic surfaces in approximately two weeks.

EXAMPLE VI Using the above testing procedure a steel coupon was immersed into my aqueous ammonia-ammonium nitrate hydrogen peroxide composition containing by weight 24 percent of NH OH, 4 percent of NH NO and 1.64 ml. of H 0 This composition exhibited freedom from corrosion during an 8 Week testing period.

The hydrogen peroxide is a 31.1 solution and has a. specific gravity of 1.147. Table I shows the results of corrosion tests on aqueous ammonia-ammonium nitrate solutions containing varying supposed inhibitors.

aorasas Table II shows the results obtained when adding con taminants to aqueous ammonia-ammonium nitrate solutions either with or without hydrogen peroxide incorporated therein.

terial sufiicient to cause corrosion of ferrous surfaces contacting said compositions.

4. The composition of claim 3 in which the soluble sulfur-containing material is selected from the group consisting of sodium sulfite and sodium sulfide.

5. A container, having internal surfaces of ferrous material having therein an ammoniacal ammonium nitrate composition containing about 0.0001 to 3% by weight of hydrogen peroxide to inhibit corrosion of said ferrous metal surfaces, said solution having about 10 to 35% byweight of ammonium hydroxide and about 1 to 35% by weight of ammonium nitrate.

6. The container of claim 5 wherein is included in the ammoniacal ammonium nitrate composition a small, contaminating amount of a soluble sulfur-containing material selected from the group consisting of sodium sulfite and sodium sulfide sufiicient to cause corrosion of ferrous surfaces contacting said composition.

Tablev II [Static-corrosion tests of hot-rolled mild steel (half mill-scaled, half-polished)] Solution 5 Contami- 1 Time H202. nant 0.1 gm. exposed. Busting m1. days Percent Percent NH4OH NH4NO3 24 4 2. 60 55 No rust, no loss.

24 4 Heavy rusting (128.3 m ld.).

24- 4 10. Heavyrusting (1.589 Ind l.).

I The'hydrogen peroxide was a 31.2% solution. Specific gravity is 1.147.

exposure.

The data above clearly show that my composition has. reduced corrosive tendencies andiis efiective in overcoming the problem of corrosion in the manufacture, transportation, storage and handling of aqueous ammonia ammonium nitrate solutions.

Iclaim:

1'. A composition consisting essentially of an ammonia-a'mrnonium nitrate aqueous solution having incorporated therein about 0.0001 to 3% by weight of hydrogen peroxide, said solution having about 10 to by weight of ammonium hydroxide and aboutl to 35% by weight of ammonium nitrate.

2'. The composition of claim 1 inwhich the amount of hydrogen peroxide incorporated is about 0.001 to 0.3%.

3. The composition of claim 1 which includes a small, contaminating amount of a soluble sulfur-containing ma- References Cited; in the tile of this patent UNITED STATES PATENTS 1,975,682 Callery Oct. 2, 1934 2,077,469 Fazel Apr. 20, 1937 2,141,189 Lind Dec. 27, 1938 2,465,228 Hein Mar. 22, 1949 2,747,734 Rose May 29, 1956 2,782,100 Greenspan Feb. 19, 1957 2,855,286 Harvey Oct. 7, 1958 2,882,237 Mahoney Apr. 14, 1959 2,936,884 Marsh et al. May 17, 1960 OTHER REFERENCES W. A. Marshall: Metal Finishing, vol. 50, November 1952, pp. 7885.

Thorpes Dictionary of Applied Chemistry, Fourth Ed, vol. VI, 1943, pp. 3456. 

1. A COMPOSITION CONTSISTING ESSENTIALLY OF AN AMMONIA-AMMONIUM NITRATE AQUEOUS SOLUTION HAVING INCORPORATED THEREIN ABOUT 0.0001 TO 3% BY WEIGHT OF HYDROGEN PEROXIDE, SAID SOLUTION HAVIN ABOUT 10 TO 35% BY WEIGHT OF AMMONIUM HYDROXIDE AND ABOUT 1 TO 35% BY WEIGHT OF AMMONIUM NITRATE. 